Fix relocation addend sign extension on 32-bit platforms (#4846)

* Fix relocation addend sign extension on 32-bit platforms

When loading relocations on 32-bit platforms, the addend is read
as uint32 and zero-extended to uint64, which corrupts negative
addends. For example, -4 (0xFFFFFFFC) becomes 4294967292 instead
of remaining -4. Use int32 with sign extension to int64, matching
the Windows code path which already handles this correctly.

core/iwasm/aot/aot_loader.c

@@ -3872,7 +3872,7 @@ load_relocation_section(const uint8 *buf, const uint8 *buf_end,
                 read_uint32(buf, buf_end, offset32);
                 relocation->relocation_offset = (uint64)offset32;
                 read_uint32(buf, buf_end, addend32);
-                relocation->relocation_addend = (uint64)addend32;
+                relocation->relocation_addend = (int64)(int32)addend32;
             }
             read_uint32(buf, buf_end, relocation->relocation_type);
             read_uint32(buf, buf_end, symbol_index);